1. Field of the Invention
This invention relates to the field of sewing machine stitch formation, and more particularly, to an arrangement for facilitating the placement of threads through superimposed plies of work fabric by the operation of a sewing machine to provide tailor tacks.
2. Description of the Prior Art
A tailor tack is a length of thread which is passed transversely through superposed plies of work fabric in such a small number of closely spaced stitches as will allow controlled lengthwise reeving of the thread when the work fabric plies are separated so that when severed between the separated plies portions of the thread will remain extending transversely through each of the work fabric plies to mark common or matching locations on the plies.
It is known to apply tailor tacks using a threaded hand sewing needle which is understandably a tedious, time consuming operation. Equally tediuous and time consuming is a known technique for using a sewing machine to produce the tailor tack stitches in which known technique each needle reciprocation of the sewing machine is manually controlled, the presser foot is lifted between tailor tacks and the work must be manually advanced through the sewing machine between desired locations for tailor tacks.
One other technique is known for utilizing a zig zag sewing machine to produce tailor tacks in which a presser device with a raised stitch supporting finger is employed. By zig zagging over the stitch supporting finger, loose stitches are formed so that the plies may be separated and the stitches severed therebetween to provide the marking threads in each of the plies. The disadvantage of this known technique stems from the relatively small amount of looseness or surplus thread which the stitch supporting finger can provide because of the necessity for the needle to pass with clearance over the finger. As a result, so small a length of surplus tailor tacking thread is provided that the threads are frequently withdrawn completely from one or both of the plies during ply separation and severance of the threads therebetween. Another disadvantage of this known technique is the limitation of thickness of the work fabrics with which it may be used without elevating the stitch supporting finger high enough to interfere with the traverse of the needle and the safety hazard occasioned by the resulting possibility of needle breakage.